Initial re-write of analysis context for the new task model

pkg/analyzer/lib/src/context/context.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library analyzer.src.context.context;
+
+import 'dart:async';
+import 'dart:collection';
+
+import 'package:analyzer/src/cancelable_future.dart';
+import 'package:analyzer/src/context/cache.dart' as cache;
+import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/constant.dart';
+import 'package:analyzer/src/generated/element.dart';
+import 'package:analyzer/src/generated/engine.dart';
+import 'package:analyzer/src/generated/error.dart';
+import 'package:analyzer/src/generated/html.dart' as ht;
+import 'package:analyzer/src/generated/java_core.dart';
+import 'package:analyzer/src/generated/java_engine.dart';
+import 'package:analyzer/src/generated/resolver.dart';
+import 'package:analyzer/src/generated/scanner.dart';
+import 'package:analyzer/src/generated/sdk.dart' show DartSdk;
+import 'package:analyzer/src/generated/source.dart';
+import 'package:analyzer/src/generated/utilities_collection.dart';
+import 'package:analyzer/src/task/dart.dart';
+import 'package:analyzer/src/task/driver.dart';
+import 'package:analyzer/src/task/manager.dart';
+import 'package:analyzer/task/dart.dart';
+import 'package:analyzer/task/general.dart';
+import 'package:analyzer/task/model.dart';
+
+/**
+ * An [AnalysisContext] in which analysis can be performed.
+ */
+class AnalysisContextImpl implements InternalAnalysisContext {
+  /**
+   * A client-provided name used to identify this context, or `null` if the
+   * client has not provided a name.
+   */
+  String name;
+
+  /**
+   * The set of analysis options controlling the behavior of this context.
+   */
+  AnalysisOptionsImpl _options = new AnalysisOptionsImpl();
+
+  /**
+   * A flag indicating whether this context is disposed.
+   */
+  bool _disposed = false;
+
+  /**
+   * A cache of content used to override the default content of a source.
+   */
+  ContentCache _contentCache = new ContentCache();
+
+  /**
+   * The source factory used to create the sources that can be analyzed in this
+   * context.
+   */
+  SourceFactory _sourceFactory;
+
+  /**
+   * The set of declared variables used when computing constant values.
+   */
+  DeclaredVariables _declaredVariables = new DeclaredVariables();
+
+  /**
+   * The partition that contains analysis results that are not shared with other
+   * contexts.
+   */
+  cache.CachePartition _privatePartition;
+
+  /**
+   * The cache in which information about the results associated with targets
+   * are stored.
+   */
+  cache.AnalysisCache _cache;
+
+  /**
+   * The task manager used to manage the tasks used to analyze code.
+   */
+  TaskManager _taskManager;
+
+  /**
+   * The analysis driver used to perform analysis.
+   */
+  AnalysisDriver _driver;
+
+  /**
+   * A list containing sources for which data should not be flushed.
+   */
+  List<Source> _priorityOrder = Source.EMPTY_ARRAY;
+
+  /**
+   * A map from all sources for which there are futures pending to a list of
+   * the corresponding PendingFuture objects.  These sources will be analyzed
+   * in the same way as priority sources, except with higher priority.
+   */
+  HashMap<Source, List<PendingFuture>> _pendingFutureSources =
+      new HashMap<Source, List<PendingFuture>>();
+
+  /**
+   * A table mapping sources to the change notices that are waiting to be
+   * returned related to that source.
+   */
+  HashMap<Source, ChangeNoticeImpl> _pendingNotices =
+      new HashMap<Source, ChangeNoticeImpl>();
+
+  /**
+   * Cached information used in incremental analysis or `null` if none.
+   */
+  IncrementalAnalysisCache _incrementalAnalysisCache;
+
+  /**
+   * The [TypeProvider] for this context, `null` if not yet created.
+   */
+  TypeProvider _typeProvider;
+
+  /**
+   * The controller for sending [SourcesChangedEvent]s.
+   */
+  StreamController<SourcesChangedEvent> _onSourcesChangedController;
+
+  /**
+   * The listeners that are to be notified when various analysis results are
+   * produced in this context.
+   */
+  List<AnalysisListener> _listeners = new List<AnalysisListener>();
+
+  /**
+   * The most recently incrementally resolved source, or `null` when it was
+   * already validated, or the most recent change was not incrementally resolved.
+   */
+  Source incrementalResolutionValidation_lastUnitSource;
+
+  /**
+   * The most recently incrementally resolved library source, or `null` when it
+   * was already validated, or the most recent change was not incrementally
+   * resolved.
+   */
+  Source incrementalResolutionValidation_lastLibrarySource;
+
+  /**
+   * The result of incremental resolution result of
+   * [incrementalResolutionValidation_lastSource].
+   */
+  CompilationUnit incrementalResolutionValidation_lastUnit;
+
+  /**
+   * A factory to override how the [ResolverVisitor] is created.
+   */
+  ResolverVisitorFactory resolverVisitorFactory;
+
+  /**
+   * A factory to override how the [TypeResolverVisitor] is created.
+   */
+  TypeResolverVisitorFactory typeResolverVisitorFactory;
+
+  /**
+   * A factory to override how [LibraryResolver] is created.
+   */
+  LibraryResolverFactory libraryResolverFactory;
+
+  /**
+   * Initialize a newly created analysis context.
+   */
+  AnalysisContextImpl() {
+    _privatePartition = new cache.UniversalCachePartition(this,
+        AnalysisOptionsImpl.DEFAULT_CACHE_SIZE,
+        new ContextRetentionPolicy(this));
+    _cache = createCacheFromSourceFactory(null);
+    _taskManager = AnalysisEngine.instance.taskManager;
+    _driver = new AnalysisDriver(_taskManager, this);
+    _onSourcesChangedController =
+        new StreamController<SourcesChangedEvent>.broadcast();
+  }
+
+  @override
+  AnalysisOptions get analysisOptions => _options;
+
+  @override
+  void set analysisOptions(AnalysisOptions options) {
+    bool needsRecompute = this._options.analyzeFunctionBodiesPredicate !=
+            options.analyzeFunctionBodiesPredicate ||
+        this._options.generateImplicitErrors !=
+            options.generateImplicitErrors ||
+        this._options.generateSdkErrors != options.generateSdkErrors ||
+        this._options.dart2jsHint != options.dart2jsHint ||
+        (this._options.hint && !options.hint) ||
+        this._options.preserveComments != options.preserveComments ||
+        this._options.enableNullAwareOperators !=
+            options.enableNullAwareOperators ||
+        this._options.enableStrictCallChecks != options.enableStrictCallChecks;
+    int cacheSize = options.cacheSize;
+    if (this._options.cacheSize != cacheSize) {
+      this._options.cacheSize = cacheSize;
+      _privatePartition.maxCacheSize = cacheSize;
+    }
+    this._options.analyzeFunctionBodiesPredicate =
+        options.analyzeFunctionBodiesPredicate;
+    this._options.generateImplicitErrors = options.generateImplicitErrors;
+    this._options.generateSdkErrors = options.generateSdkErrors;
+    this._options.dart2jsHint = options.dart2jsHint;
+    this._options.enableNullAwareOperators = options.enableNullAwareOperators;
+    this._options.enableStrictCallChecks = options.enableStrictCallChecks;
+    this._options.hint = options.hint;
+    this._options.incremental = options.incremental;
+    this._options.incrementalApi = options.incrementalApi;
+    this._options.incrementalValidation = options.incrementalValidation;
+    this._options.lint = options.lint;
+    this._options.preserveComments = options.preserveComments;
+    if (needsRecompute) {
+      _invalidateAllLocalResolutionInformation(false);
+    }
+  }
+
+  @override
+  void set analysisPriorityOrder(List<Source> sources) {
+    if (sources == null || sources.isEmpty) {
+      _priorityOrder = Source.EMPTY_ARRAY;
+    } else {
+      while (sources.remove(null)) {
+        // Nothing else to do.
+      }
+      if (sources.isEmpty) {
+        _priorityOrder = Source.EMPTY_ARRAY;
+      } else {
+        _priorityOrder = sources;
+      }
+    }
+  }
+
+  @override
+  set contentCache(ContentCache value) {
+    _contentCache = value;
+  }
+
+  @override
+  DeclaredVariables get declaredVariables => _declaredVariables;
+
+  @override
+  List<AnalysisTarget> get explicitTargets {
+    List<AnalysisTarget> targets = <AnalysisTarget>[];
+    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+    while (iterator.moveNext()) {
+      if (iterator.value.explicitlyAdded) {
+        targets.add(iterator.key);
+      }
+    }
+    return targets;
+  }
+
+  @override
+  List<Source> get htmlSources => _getSources(SourceKind.HTML);
+
+  @override
+  bool get isDisposed => _disposed;
+
+  @override
+  List<Source> get launchableClientLibrarySources {
+    // TODO(brianwilkerson) This needs to filter out libraries that do not
+    // reference dart:html, either directly or indirectly.
+    List<Source> sources = new List<Source>();
+    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+    while (iterator.moveNext()) {
+      AnalysisTarget target = iterator.key;
+      cache.CacheEntry entry = iterator.value;
+      if (target is Source &&
+          entry.getValue(SOURCE_KIND) == SourceKind.LIBRARY &&
+          !target.isInSystemLibrary) {
+//          DartEntry dartEntry = (DartEntry) sourceEntry;
+//          if (dartEntry.getValue(DartEntry.IS_LAUNCHABLE) && !dartEntry.getValue(DartEntry.IS_CLIENT)) {
+        sources.add(target);
+//          }
+      }
+    }
+    return sources;
+  }
+
+  @override
+  List<Source> get launchableServerLibrarySources {
+    // TODO(brianwilkerson) This needs to filter out libraries that reference
+    // dart:html, either directly or indirectly.
+    List<Source> sources = new List<Source>();
+    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+    while (iterator.moveNext()) {
+      AnalysisTarget target = iterator.key;
+      cache.CacheEntry entry = iterator.value;
+      if (target is Source &&
+          entry.getValue(SOURCE_KIND) == SourceKind.LIBRARY &&
+          !target.isInSystemLibrary) {
+//          DartEntry dartEntry = (DartEntry) sourceEntry;
+//          if (dartEntry.getValue(DartEntry.IS_LAUNCHABLE) && !dartEntry.getValue(DartEntry.IS_CLIENT)) {
+        sources.add(target);
+//          }
+      }
+    }
+    return sources;
+  }
+
+  @override
+  List<Source> get librarySources => _getSources(SourceKind.LIBRARY);
+
+  @override
+  Stream<SourcesChangedEvent> get onSourcesChanged =>
+      _onSourcesChangedController.stream;
+
+  /**
+   * Make _pendingFutureSources available to unit tests.
+   */
+  HashMap<Source, List<PendingFuture>> get pendingFutureSources_forTesting =>
+      _pendingFutureSources;
+
+  @override
+  List<Source> get prioritySources => _priorityOrder;
+
+  @override
+  List<AnalysisTarget> get priorityTargets => prioritySources;
+
+  @override
+  List<Source> get refactoringUnsafeSources {
+    // TODO(brianwilkerson) Implement this.
+    List<Source> sources = new List<Source>();
+//    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+//    while (iterator.moveNext()) {
+//      cache.CacheEntry entry = iterator.value;
+//      AnalysisTarget target = iterator.key;
+//      if (target is Source &&
+//          !target.isInSystemLibrary &&
+//          !entry.isRefactoringSafe) {
+//        sources.add(target);
+//      }
+//    }
+    return sources;
+  }
+
+  @override
+  SourceFactory get sourceFactory => _sourceFactory;
+
+  @override
+  void set sourceFactory(SourceFactory factory) {
+    if (identical(_sourceFactory, factory)) {
+      return;
+    } else if (factory.context != null) {
+      throw new IllegalStateException(
+          "Source factories cannot be shared between contexts");
+    }
+    if (_sourceFactory != null) {
+      _sourceFactory.context = null;
+    }
+    factory.context = this;
+    _sourceFactory = factory;
+    _cache = createCacheFromSourceFactory(factory);
+    _invalidateAllLocalResolutionInformation(true);
+  }
+
+  @override
+  List<Source> get sources {
+    List<Source> sources = new List<Source>();
+    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+    while (iterator.moveNext()) {
+      AnalysisTarget target = iterator.key;
+      if (target is Source) {
+        sources.add(target);
+      }
+    }
+    return sources;
+  }
+
+  /**
+   * Return a list of the sources that would be processed by
+   * [performAnalysisTask]. This method duplicates, and must therefore be kept
+   * in sync with, [getNextAnalysisTask]. This method is intended to be used for
+   * testing purposes only.
+   */
+  List<Source> get sourcesNeedingProcessing {
+    HashSet<Source> sources = new HashSet<Source>();
+    bool hintsEnabled = _options.hint;
+    bool lintsEnabled = _options.lint;
+
+    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+    while (iterator.moveNext()) {
+      AnalysisTarget target = iterator.key;
+      if (target is Source) {
+        _getSourcesNeedingProcessing(
+            target, iterator.value, false, hintsEnabled, lintsEnabled, sources);
+      }
+    }
+    return new List<Source>.from(sources);
+  }
+
+  @override
+  AnalysisContextStatistics get statistics {
+    AnalysisContextStatisticsImpl statistics =
+        new AnalysisContextStatisticsImpl();
+    // TODO(brianwilkerson) Implement this.
+//    visitCacheItems(statistics._internalPutCacheItem);
+//    statistics.partitionData = _cache.partitionData;
+    return statistics;
+  }
+
+  IncrementalAnalysisCache get test_incrementalAnalysisCache {
+    return _incrementalAnalysisCache;
+  }
+
+  set test_incrementalAnalysisCache(IncrementalAnalysisCache value) {
+    _incrementalAnalysisCache = value;
+  }
+
+  List<Source> get test_priorityOrder => _priorityOrder;
+
+  @override
+  TypeProvider get typeProvider {
+    if (_typeProvider != null) {
+      return _typeProvider;
+    }
+    Source coreSource = sourceFactory.forUri(DartSdk.DART_CORE);
+    if (coreSource == null) {
+      throw new AnalysisException("Could not create a source for dart:core");
+    }
+    LibraryElement coreElement = computeLibraryElement(coreSource);
+    if (coreElement == null) {
+      throw new AnalysisException("Could not create an element for dart:core");
+    }
+    Source asyncSource = sourceFactory.forUri(DartSdk.DART_ASYNC);
+    if (asyncSource == null) {
+      throw new AnalysisException("Could not create a source for dart:async");
+    }
+    LibraryElement asyncElement = computeLibraryElement(asyncSource);
+    if (asyncElement == null) {
+      throw new AnalysisException("Could not create an element for dart:async");
+    }
+    _typeProvider = new TypeProviderImpl(coreElement, asyncElement);
+    return _typeProvider;
+  }
+
+  /**
+   * Sets the [TypeProvider] for this context.
+   */
+  void set typeProvider(TypeProvider typeProvider) {
+    _typeProvider = typeProvider;
+  }
+
+  /**
+   * Return `true` if the (new) task model should be used to perform analysis.
+   */
+  bool get useTaskModel => AnalysisEngine.instance.useTaskModel;
+
+  @override
+  void addListener(AnalysisListener listener) {
+    if (!_listeners.contains(listener)) {
+      _listeners.add(listener);
+    }
+  }
+
+  @override
+  void addSourceInfo(Source source, SourceEntry info) {
+    // TODO(brianwilkerson) This method needs to be replaced by something that
+    // will copy CacheEntry's.
+//    _cache.put(source, info);
+  }
+
+  @override
+  void applyAnalysisDelta(AnalysisDelta delta) {
+    ChangeSet changeSet = new ChangeSet();
+    delta.analysisLevels.forEach((Source source, AnalysisLevel level) {
+      if (level == AnalysisLevel.NONE) {
+        changeSet.removedSource(source);
+      } else {
+        changeSet.addedSource(source);
+      }
+    });
+    applyChanges(changeSet);
+  }
+
+  @override
+  void applyChanges(ChangeSet changeSet) {
+    if (changeSet.isEmpty) {
+      return;
+    }
+    //
+    // First, compute the list of sources that have been removed.
+    //
+    List<Source> removedSources =
+        new List<Source>.from(changeSet.removedSources);
+    for (SourceContainer container in changeSet.removedContainers) {
+      _addSourcesInContainer(removedSources, container);
+    }
+    //
+    // Then determine which cached results are no longer valid.
+    //
+    for (Source source in changeSet.addedSources) {
+      _sourceAvailable(source);
+    }
+    for (Source source in changeSet.changedSources) {
+      if (_contentCache.getContents(source) != null) {
+        // This source is overridden in the content cache, so the change will
+        // have no effect. Just ignore it to avoid wasting time doing
+        // re-analysis.
+        continue;
+      }
+      _sourceChanged(source);
+    }
+    changeSet.changedContents.forEach((Source key, String value) {
+      _contentsChanged(key, value, false);
+    });
+    changeSet.changedRanges
+        .forEach((Source source, ChangeSet_ContentChange change) {
+      _contentRangeChanged(source, change.contents, change.offset,
+          change.oldLength, change.newLength);
+    });
+    for (Source source in changeSet.deletedSources) {
+      _sourceDeleted(source);
+    }
+    for (Source source in removedSources) {
+      _sourceRemoved(source);
+    }
+    _onSourcesChangedController.add(new SourcesChangedEvent(changeSet));
+  }
+
+  @override
+  String computeDocumentationComment(Element element) {
+    if (element == null) {
+      return null;
+    }
+    Source source = element.source;
+    if (source == null) {
+      return null;
+    }
+    CompilationUnit unit = parseCompilationUnit(source);
+    if (unit == null) {
+      return null;
+    }
+    NodeLocator locator = new NodeLocator.con1(element.nameOffset);
+    AstNode nameNode = locator.searchWithin(unit);
+    while (nameNode != null) {
+      if (nameNode is AnnotatedNode) {
+        Comment comment = nameNode.documentationComment;
+        if (comment == null) {
+          return null;
+        }
+        StringBuffer buffer = new StringBuffer();
+        List<Token> tokens = comment.tokens;
+        for (int i = 0; i < tokens.length; i++) {
+          if (i > 0) {
+            buffer.write("\n");
+          }
+          buffer.write(tokens[i].lexeme);
+        }
+        return buffer.toString();
+      }
+      nameNode = nameNode.parent;
+    }
+    return null;
+  }
+
+  @override
+  List<AnalysisError> computeErrors(Source source) =>
+      _computeResult(source, DART_ERRORS);
+
+  @override
+  List<Source> computeExportedLibraries(Source source) =>
+      _computeResult(source, EXPORTED_LIBRARIES);
+
+  @override
+  // TODO(brianwilkerson) Implement this.
+  HtmlElement computeHtmlElement(Source source) => null;
+
+  @override
+  List<Source> computeImportedLibraries(Source source) => _computeResult(
+      source, IMPORTED_LIBRARIES);
+
+  @override
+  SourceKind computeKindOf(Source source) =>
+      _computeResult(source, SOURCE_KIND);
+
+  @override
+  LibraryElement computeLibraryElement(Source source) =>
+      _computeResult(source, LIBRARY_ELEMENT); //_computeResult(source, HtmlEntry.ELEMENT);
+
+  @override
+  LineInfo computeLineInfo(Source source) => _computeResult(source, LINE_INFO);
+
+  @override
+  @deprecated
+  CompilationUnit computeResolvableCompilationUnit(Source source) {
+    return null;
+  }
+
+  @override
+  CancelableFuture<CompilationUnit> computeResolvedCompilationUnitAsync(
+      Source unitSource, Source librarySource) {
+    // TODO(brianwilkerson) Implement this.
+    return new CancelableFuture<CompilationUnit>(() => null);
+//    return new _AnalysisFutureHelper<CompilationUnit>(this).computeAsync(
+//        unitSource, (SourceEntry sourceEntry) {
+//      if (sourceEntry is DartEntry) {
+//        if (sourceEntry.getStateInLibrary(
+//                DartEntry.RESOLVED_UNIT, librarySource) ==
+//            CacheState.ERROR) {
+//          throw sourceEntry.exception;
+//        }
+//        return sourceEntry.getValueInLibrary(
+//            DartEntry.RESOLVED_UNIT, librarySource);
+//      }
+//      throw new AnalysisNotScheduledError();
+//    });
+  }
+
+  /**
+   * Create an analysis cache based on the given source [factory].
+   */
+  cache.AnalysisCache createCacheFromSourceFactory(SourceFactory factory) {
+    if (factory == null) {
+      return new cache.AnalysisCache(<cache.CachePartition>[_privatePartition]);
+    }
+    DartSdk sdk = factory.dartSdk;
+    if (sdk == null) {
+      return new cache.AnalysisCache(<cache.CachePartition>[_privatePartition]);
+    }
+    return new cache.AnalysisCache(<cache.CachePartition>[
+      AnalysisEngine.instance.partitionManager_new.forSdk(sdk),
+      _privatePartition
+    ]);
+  }
+
+  @override
+  void dispose() {
+    _disposed = true;
+    for (List<PendingFuture> pendingFutures in _pendingFutureSources.values) {
+      for (PendingFuture pendingFuture in pendingFutures) {
+        pendingFuture.forciblyComplete();
+      }
+    }
+    _pendingFutureSources.clear();
+  }
+
+  @override
+  List<CompilationUnit> ensureResolvedDartUnits(Source unitSource) {
+    // TODO(brianwilkerson) Implement this.
+    return null;
+//    cache.CacheEntry entry = _cache.get(unitSource);
+//    // Check every library.
+//    List<CompilationUnit> units = <CompilationUnit>[];
+//    List<Source> containingLibraries = entry.containingLibraries;
+//    for (Source librarySource in containingLibraries) {
+//      CompilationUnit unit =
+//          entry.getValueInLibrary(DartEntry.RESOLVED_UNIT, librarySource);
+//      if (unit == null) {
+//        units = null;
+//        break;
+//      }
+//      units.add(unit);
+//    }
+//    // Invalidate the flushed RESOLVED_UNIT to force it eventually.
+//    if (units == null) {
+//      bool shouldBeScheduled = false;
+//      for (Source librarySource in containingLibraries) {
+//        if (entry.getStateInLibrary(DartEntry.RESOLVED_UNIT, librarySource) ==
+//            CacheState.FLUSHED) {
+//          entry.setStateInLibrary(
+//              DartEntry.RESOLVED_UNIT, librarySource, CacheState.INVALID);
+//          shouldBeScheduled = true;
+//        }
+//      }
+//      if (shouldBeScheduled) {
+//        _workManager.add(unitSource, SourcePriority.UNKNOWN);
+//      }
+//      // We cannot provide resolved units right now,
+//      // but the future analysis will.
+//      return null;
+//    }
+//    // done
+//    return units;
+  }
+
+  @override
+  bool exists(Source source) {
+    if (source == null) {
+      return false;
+    }
+    if (_contentCache.getContents(source) != null) {
+      return true;
+    }
+    return source.exists();
+  }
+
+  Element findElementById(int id) {
+    // TODO(brianwilkerson) Implement this.
+    return null;
+//    _ElementByIdFinder finder = new _ElementByIdFinder(id);
+//    try {
+//      MapIterator<AnalysisTarget, cache.CacheEntry> iterator =
+//          _cache.iterator();
+//      while (iterator.moveNext()) {
+//        cache.CacheEntry entry = iterator.value;
+//        if (entry.getValue(SOURCE_KIND) == SourceKind.LIBRARY) {
+//          DartEntry dartEntry = entry;
+//          LibraryElement library = dartEntry.getValue(DartEntry.ELEMENT);
+//          if (library != null) {
+//            library.accept(finder);
+//          }
+//        }
+//      }
+//    } on _ElementByIdFinderException {
+//      return finder.result;
+//    }
+//    return null;
+  }
+
+  @override
+  cache.CacheEntry getCacheEntry(AnalysisTarget target) {
+    cache.CacheEntry entry = _cache.get(target);
+    if (entry == null) {
+      entry = new cache.CacheEntry();
+      _cache.put(target, entry);
+    }
+    return entry;
+  }
+
+  @override
+  CompilationUnitElement getCompilationUnitElement(
+      Source unitSource, Source librarySource) {
+    AnalysisTarget target = new LibrarySpecificUnit(librarySource, unitSource);
+    return _getResult(target, COMPILATION_UNIT_ELEMENT);
+  }
+
+  @override
+  TimestampedData<String> getContents(Source source) {
+    String contents = _contentCache.getContents(source);
+    if (contents != null) {
+      return new TimestampedData<String>(
+          _contentCache.getModificationStamp(source), contents);
+    }
+    return source.contents;
+  }
+
+  @override
+  InternalAnalysisContext getContextFor(Source source) {
+    InternalAnalysisContext context = _cache.getContextFor(source);
+    return context == null ? this : context;
+  }
+
+  @override
+  Element getElement(ElementLocation location) {
+    // TODO(brianwilkerson) This should not be a "get" method.
+    try {
+      List<String> components = location.components;
+      Source source = _computeSourceFromEncoding(components[0]);
+      String sourceName = source.shortName;
+      if (AnalysisEngine.isDartFileName(sourceName)) {
+        ElementImpl element = computeLibraryElement(source) as ElementImpl;
+        for (int i = 1; i < components.length; i++) {
+          if (element == null) {
+            return null;
+          }
+          element = element.getChild(components[i]);
+        }
+        return element;
+      }
+      if (AnalysisEngine.isHtmlFileName(sourceName)) {
+        return computeHtmlElement(source);
+      }
+    } catch (exception) {
+      // If the location cannot be decoded for some reason then the underlying
+      // cause should have been logged already and we can fall though to return
+      // null.
+    }
+    return null;
+  }
+
+  @override
+  AnalysisErrorInfo getErrors(Source source) => _getResult(source, DART_ERRORS);
+
+  @override
+  HtmlElement getHtmlElement(Source source) {
+    // TODO(brianwilkerson) Implement this.
+//    SourceEntry sourceEntry = getReadableSourceEntryOrNull(source);
+//    if (sourceEntry is HtmlEntry) {
+//      return sourceEntry.getValue(HtmlEntry.ELEMENT);
+//    }
+    return null;
+  }
+
+  @override
+  List<Source> getHtmlFilesReferencing(Source source) {
+    SourceKind sourceKind = getKindOf(source);
+    if (sourceKind == null) {
+      return Source.EMPTY_ARRAY;
+    }
+    List<Source> htmlSources = new List<Source>();
+    while (true) {
+      if (sourceKind == SourceKind.PART) {
+        List<Source> librarySources = getLibrariesContaining(source);
+        MapIterator<AnalysisTarget, cache.CacheEntry> iterator =
+            _cache.iterator();
+        while (iterator.moveNext()) {
+          cache.CacheEntry entry = iterator.value;
+          if (entry.getValue(SOURCE_KIND) == SourceKind.HTML) {
+            List<Source> referencedLibraries =
+                (entry as HtmlEntry).getValue(HtmlEntry.REFERENCED_LIBRARIES);
+            if (_containsAny(referencedLibraries, librarySources)) {
+              htmlSources.add(iterator.key);
+            }
+          }
+        }
+      } else {
+        MapIterator<AnalysisTarget, cache.CacheEntry> iterator =
+            _cache.iterator();
+        while (iterator.moveNext()) {
+          cache.CacheEntry entry = iterator.value;
+          if (entry.getValue(SOURCE_KIND) == SourceKind.HTML) {
+            List<Source> referencedLibraries =
+                (entry as HtmlEntry).getValue(HtmlEntry.REFERENCED_LIBRARIES);
+            if (_contains(referencedLibraries, source)) {
+              htmlSources.add(iterator.key);
+            }
+          }
+        }
+      }
+      break;
+    }
+    if (htmlSources.isEmpty) {
+      return Source.EMPTY_ARRAY;
+    }
+    return htmlSources;
+  }
+
+  @override
+  SourceKind getKindOf(Source source) => _getResult(source, SOURCE_KIND);
+
+  @override
+  List<Source> getLibrariesContaining(Source source) {
+    // TODO(brianwilkerson) Implement this.
+//    cache.CacheEntry sourceEntry = _cache.get(source);
+//    if (sourceEntry is DartEntry) {
+//      return sourceEntry.containingLibraries;
+//    }
+    return Source.EMPTY_ARRAY;
+  }
+
+  @override
+  List<Source> getLibrariesDependingOn(Source librarySource) {
+    List<Source> dependentLibraries = new List<Source>();
+    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+    while (iterator.moveNext()) {
+      cache.CacheEntry entry = iterator.value;
+      if (entry.getValue(SOURCE_KIND) == SourceKind.LIBRARY) {
+        if (_contains(entry.getValue(EXPORTED_LIBRARIES), librarySource)) {
+          dependentLibraries.add(iterator.key);
+        }
+        if (_contains(entry.getValue(IMPORTED_LIBRARIES), librarySource)) {
+          dependentLibraries.add(iterator.key);
+        }
+      }
+    }
+    if (dependentLibraries.isEmpty) {
+      return Source.EMPTY_ARRAY;
+    }
+    return dependentLibraries;
+  }
+
+  @override
+  List<Source> getLibrariesReferencedFromHtml(Source htmlSource) {
+    // TODO(brianwilkerson) Implement this.
+//    cache.CacheEntry entry = getReadableSourceEntryOrNull(htmlSource);
+//    if (entry is HtmlEntry) {
+//      HtmlEntry htmlEntry = entry;
+//      return htmlEntry.getValue(HtmlEntry.REFERENCED_LIBRARIES);
+//    }
+    return Source.EMPTY_ARRAY;
+  }
+
+  @override
+  LibraryElement getLibraryElement(Source source) =>
+      _getResult(source, LIBRARY_ELEMENT);
+
+  @override
+  LineInfo getLineInfo(Source source) => _getResult(source, LINE_INFO);
+
+  @override
+  int getModificationStamp(Source source) {
+    int stamp = _contentCache.getModificationStamp(source);
+    if (stamp != null) {
+      return stamp;
+    }
+    return source.modificationStamp;
+  }
+
+  @override
+  Namespace getPublicNamespace(LibraryElement library) {
+    // TODO(brianwilkerson) Rename this to not start with 'get'.
+    // Note that this is not part of the API of the interface.
+    // TODO(brianwilkerson) The public namespace used to be cached, but no is.

[scheglov, 2015/04/20 03:44:50]

The only client of this method is NamespaceBuilder._createExportMapping(), and
it is not used with tasks - instead we compute export namespace once using
BuildExportNamespaceTask and reuse in scopes.

[Brian Wilkerson, 2015/04/20 15:00:36]

Clean-up (by someone) in a later CL.

+    NamespaceBuilder builder = new NamespaceBuilder();
+    return builder.createPublicNamespaceForLibrary(library);
+  }
+
+  /**
+   * Return the cache entry associated with the given [source], or `null` if
+   * there is no entry associated with the source.
+   */
+  cache.CacheEntry getReadableSourceEntryOrNull(Source source) =>
+      _cache.get(source);
+
+  @override
+  CompilationUnit getResolvedCompilationUnit(
+      Source unitSource, LibraryElement library) {
+    if (library == null) {
+      return null;
+    }
+    return getResolvedCompilationUnit2(unitSource, library.source);
+  }
+
+  @override
+  CompilationUnit getResolvedCompilationUnit2(
+      Source unitSource, Source librarySource) => _getResult(
+          new LibrarySpecificUnit(librarySource, unitSource), RESOLVED_UNIT);
+
+  @override
+  ht.HtmlUnit getResolvedHtmlUnit(Source htmlSource) {
+    // TODO(brianwilkerson) Implement this.
+//    SourceEntry sourceEntry = getReadableSourceEntryOrNull(htmlSource);
+//    if (sourceEntry is HtmlEntry) {
+//      HtmlEntry htmlEntry = sourceEntry;
+//      return htmlEntry.getValue(HtmlEntry.RESOLVED_UNIT);
+//    }
+    return null;
+  }
+
+  @override
+  List<Source> getSourcesWithFullName(String path) {
+    List<Source> sources = <Source>[];
+    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+    while (iterator.moveNext()) {
+      AnalysisTarget target = iterator.key;
+      if (target is Source && target.fullName == path) {
+        sources.add(target);
+      }
+    }
+    return sources;
+  }
+
+  @override
+  bool handleContentsChanged(
+      Source source, String originalContents, String newContents, bool notify) {
+    cache.CacheEntry entry = _cache.get(source);
+    if (entry == null) {
+      return false;
+    }
+    bool changed = newContents != originalContents;
+    if (newContents != null) {
+      if (newContents != originalContents) {
+        _incrementalAnalysisCache =
+            IncrementalAnalysisCache.clear(_incrementalAnalysisCache, source);
+        if (!analysisOptions.incremental ||
+            !_tryPoorMansIncrementalResolution(source, newContents)) {
+          _sourceChanged(source);
+        }
+        entry.modificationTime = _contentCache.getModificationStamp(source);
+        entry.setValue(CONTENT, newContents);
+      } else {
+        entry.modificationTime = _contentCache.getModificationStamp(source);
+      }
+    } else if (originalContents != null) {
+      _incrementalAnalysisCache =
+          IncrementalAnalysisCache.clear(_incrementalAnalysisCache, source);
+      changed = newContents != originalContents;
+      // We are removing the overlay for the file, check if the file's
+      // contents is the same as it was in the overlay.
+      try {
+        TimestampedData<String> fileContents = getContents(source);
+        String fileContentsData = fileContents.data;
+        if (fileContentsData == originalContents) {
+          entry.setValue(CONTENT, fileContentsData);
+          entry.modificationTime = fileContents.modificationTime;
+          changed = false;
+        }
+      } catch (e) {}
+      // If not the same content (e.g. the file is being closed without save),
+      // then force analysis.
+      if (changed) {
+        _sourceChanged(source);
+      }
+    }
+    if (notify && changed) {
+      _onSourcesChangedController
+          .add(new SourcesChangedEvent.changedContent(source, newContents));
+    }
+    return changed;
+  }
+
+  /**
+   * Invalidates hints in the given [librarySource] and included parts.
+   */
+  void invalidateLibraryHints(Source librarySource) {
+    cache.CacheEntry entry = _cache.get(librarySource);
+    // Prepare sources to invalidate hints in.
+    List<Source> sources = <Source>[librarySource];
+    sources.addAll(entry.getValue(INCLUDED_PARTS));
+    // Invalidate hints.
+    for (Source source in sources) {
+      LibrarySpecificUnit unitTarget =
+          new LibrarySpecificUnit(librarySource, source);
+      cache.CacheEntry unitEntry = _cache.get(unitTarget);
+      if (unitEntry.getState(HINTS) == CacheState.VALID) {
+        unitEntry.setState(HINTS, CacheState.INVALID);
+      }
+    }
+  }
+
+  @override
+  bool isClientLibrary(Source librarySource) {
+    cache.CacheEntry entry = _cache.get(librarySource);
+    return entry.getValue(IS_CLIENT) && entry.getValue(IS_LAUNCHABLE);
+  }
+
+  @override
+  bool isServerLibrary(Source librarySource) {
+    cache.CacheEntry entry = _cache.get(librarySource);
+    return !entry.getValue(IS_CLIENT) && entry.getValue(IS_LAUNCHABLE);
+  }
+
+  @override
+  CompilationUnit parseCompilationUnit(Source source) {
+    if (!AnalysisEngine.isDartFileName(source.shortName)) {
+      return null;
+    }
+    return _computeResult(source, PARSED_UNIT);
+  }
+
+  @override
+  ht.HtmlUnit parseHtmlUnit(Source source) {
+    if (!AnalysisEngine.isHtmlFileName(source.shortName)) {
+      return null;
+    }
+    // TODO(brianwilkerson) Implement HTML analysis.
+    return null; //_computeResult(source, null);
+  }
+
+  @override
+  AnalysisResult performAnalysisTask() {
+    return PerformanceStatistics.performAnaysis.makeCurrentWhile(() {
+      bool done = !_driver.performAnalysisTask();
+      if (done) {
+        done = !_validateCacheConsistency();
+      }
+      List<ChangeNotice> notices = _getChangeNotices(done);
+      if (notices != null) {
+        int noticeCount = notices.length;
+        for (int i = 0; i < noticeCount; i++) {
+          ChangeNotice notice = notices[i];
+          _notifyErrors(notice.source, notice.errors, notice.lineInfo);
+        }
+      }
+      return new AnalysisResult(notices, -1, '', -1);
+    });
+  }
+
+  @override
+  void recordLibraryElements(Map<Source, LibraryElement> elementMap) {
+    elementMap.forEach((Source librarySource, LibraryElement library) {
+      //
+      // Cache the element in the library's info.
+      //
+      cache.CacheEntry entry = getCacheEntry(librarySource);
+      entry.setValue(BUILD_DIRECTIVES_ERRORS, AnalysisError.NO_ERRORS);
+      entry.setValue(
+          BUILD_FUNCTION_TYPE_ALIASES_ERRORS, AnalysisError.NO_ERRORS);
+      entry.setValue(BUILD_LIBRARY_ERRORS, AnalysisError.NO_ERRORS);
+      // CLASS_ELEMENTS
+      entry.setValue(COMPILATION_UNIT_ELEMENT, library.definingCompilationUnit);
+      // CONSTRUCTORS
+      // CONSTRUCTORS_ERRORS
+      entry.setState(CONTENT, CacheState.FLUSHED);
+      entry.setValue(EXPORTED_LIBRARIES, Source.EMPTY_ARRAY);
+      // EXPORT_SOURCE_CLOSURE
+      entry.setValue(IMPORTED_LIBRARIES, Source.EMPTY_ARRAY);
+      // IMPORT_SOURCE_CLOSURE
+      entry.setValue(INCLUDED_PARTS, Source.EMPTY_ARRAY);
+      entry.setValue(IS_CLIENT, true);
+      entry.setValue(IS_LAUNCHABLE, false);
+      entry.setValue(LIBRARY_ELEMENT, library);
+      entry.setValue(LIBRARY_ELEMENT1, library);
+      entry.setValue(LIBRARY_ELEMENT2, library);
+      entry.setValue(LIBRARY_ELEMENT3, library);
+      entry.setValue(LIBRARY_ELEMENT4, library);
+      entry.setValue(LIBRARY_ELEMENT5, library);
+      entry.setValue(LINE_INFO, new LineInfo(<int>[0]));
+      entry.setValue(PARSE_ERRORS, AnalysisError.NO_ERRORS);
+      entry.setState(PARSED_UNIT, CacheState.FLUSHED);
+      entry.setState(RESOLVE_TYPE_NAMES_ERRORS, CacheState.FLUSHED);
+      entry.setValue(SCAN_ERRORS, AnalysisError.NO_ERRORS);
+      entry.setValue(SOURCE_KIND, SourceKind.LIBRARY);
+      entry.setState(TOKEN_STREAM, CacheState.FLUSHED);
+      entry.setValue(UNITS, <Source>[librarySource]);
+
+      LibrarySpecificUnit unit =
+          new LibrarySpecificUnit(librarySource, librarySource);
+      entry = getCacheEntry(unit);
+      entry.setValue(HINTS, AnalysisError.NO_ERRORS);
+      // dartEntry.setValue(LINTS, AnalysisError.NO_ERRORS);
+      entry.setState(RESOLVE_REFERENCES_ERRORS, CacheState.FLUSHED);
+      entry.setState(RESOLVED_UNIT, CacheState.FLUSHED);
+      entry.setState(RESOLVED_UNIT1, CacheState.FLUSHED);
+      entry.setState(RESOLVED_UNIT2, CacheState.FLUSHED);
+      entry.setState(RESOLVED_UNIT3, CacheState.FLUSHED);
+      entry.setState(RESOLVED_UNIT4, CacheState.FLUSHED);
+      entry.setState(RESOLVED_UNIT5, CacheState.FLUSHED);
+      // USED_IMPORTED_ELEMENTS
+      // USED_LOCAL_ELEMENTS
+      entry.setValue(VERIFY_ERRORS, AnalysisError.NO_ERRORS);
+    });
+
+    cache.CacheEntry entry = getCacheEntry(AnalysisContextTarget.request);
+    entry.setValue(TYPE_PROVIDER, typeProvider);
+  }
+
+  @override
+  void removeListener(AnalysisListener listener) {
+    _listeners.remove(listener);
+  }
+
+  @override
+  CompilationUnit resolveCompilationUnit(
+      Source unitSource, LibraryElement library) {
+    if (library == null) {
+      return null;
+    }
+    return resolveCompilationUnit2(unitSource, library.source);
+  }
+
+  @override
+  CompilationUnit resolveCompilationUnit2(
+      Source unitSource, Source librarySource) => _computeResult(
+          new LibrarySpecificUnit(librarySource, unitSource), RESOLVED_UNIT);
+
+  @override
+  ht.HtmlUnit resolveHtmlUnit(Source htmlSource) {
+    computeHtmlElement(htmlSource);
+    return parseHtmlUnit(htmlSource);
+  }
+
+  @override
+  void setChangedContents(Source source, String contents, int offset,
+      int oldLength, int newLength) {
+    if (_contentRangeChanged(source, contents, offset, oldLength, newLength)) {
+      _onSourcesChangedController.add(new SourcesChangedEvent.changedRange(
+          source, contents, offset, oldLength, newLength));
+    }
+  }
+
+  @override
+  void setContents(Source source, String contents) {
+    _contentsChanged(source, contents, true);
+  }
+
+  @override
+  void visitCacheItems(void callback(Source source, SourceEntry dartEntry,
+      DataDescriptor rowDesc, CacheState state)) {
+    // TODO(brianwilkerson) Figure out where this is used and adjust the call
+    // sites to use CacheEntry's.
+//    bool hintsEnabled = _options.hint;
+//    bool lintsEnabled = _options.lint;
+//    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+//    while (iterator.moveNext()) {
+//      Source source = iterator.key;
+//      cache.CacheEntry sourceEntry = iterator.value;
+//      for (DataDescriptor descriptor in sourceEntry.descriptors) {
+//        if (descriptor == DartEntry.SOURCE_KIND) {
+//          // The source kind is always valid, so the state isn't interesting.
+//          continue;
+//        } else if (descriptor == DartEntry.CONTAINING_LIBRARIES) {
+//          // The list of containing libraries is always valid, so the state
+//          // isn't interesting.
+//          continue;
+//        } else if (descriptor == DartEntry.PUBLIC_NAMESPACE) {
+//          // The public namespace isn't computed by performAnalysisTask()
+//          // and therefore isn't interesting.
+//          continue;
+//        } else if (descriptor == HtmlEntry.HINTS) {
+//          // We are not currently recording any hints related to HTML.
+//          continue;
+//        }
+//        callback(
+//            source, sourceEntry, descriptor, sourceEntry.getState(descriptor));
+//      }
+//      if (sourceEntry is DartEntry) {
+//        // get library-specific values
+//        List<Source> librarySources = getLibrariesContaining(source);
+//        for (Source librarySource in librarySources) {
+//          for (DataDescriptor descriptor in sourceEntry.libraryDescriptors) {
+//            if (descriptor == DartEntry.BUILT_ELEMENT ||
+//                descriptor == DartEntry.BUILT_UNIT) {
+//              // These values are not currently being computed, so their state
+//              // is not interesting.
+//              continue;
+//            } else if (!sourceEntry.explicitlyAdded &&
+//                !_generateImplicitErrors &&
+//                (descriptor == DartEntry.VERIFICATION_ERRORS ||
+//                    descriptor == DartEntry.HINTS ||
+//                    descriptor == DartEntry.LINTS)) {
+//              continue;
+//            } else if (source.isInSystemLibrary &&
+//                !_generateSdkErrors &&
+//                (descriptor == DartEntry.VERIFICATION_ERRORS ||
+//                    descriptor == DartEntry.HINTS ||
+//                    descriptor == DartEntry.LINTS)) {
+//              continue;
+//            } else if (!hintsEnabled && descriptor == DartEntry.HINTS) {
+//              continue;
+//            } else if (!lintsEnabled && descriptor == DartEntry.LINTS) {
+//              continue;
+//            }
+//            callback(librarySource, sourceEntry, descriptor,
+//                sourceEntry.getStateInLibrary(descriptor, librarySource));
+//          }
+//        }
+//      }
+//    }
+  }
+
+  /**
+   * Visit all entries of the content cache.
+   */
+  void visitContentCache(ContentCacheVisitor visitor) {
+    _contentCache.accept(visitor);
+  }
+
+  /**
+   * Add all of the sources contained in the given source [container] to the
+   * given list of [sources].
+   */
+  void _addSourcesInContainer(List<Source> sources, SourceContainer container) {
+    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+    while (iterator.moveNext()) {
+      Source source = iterator.key;
+      if (container.contains(source)) {
+        sources.add(source);
+      }
+    }
+  }
+
+  /**
+   * Return the priority that should be used when the source associated with
+   * the given [entry] is added to the work manager.
+   */
+  SourcePriority _computePriority(cache.CacheEntry entry) {
+    // Used in commented out code.
+    SourceKind kind = entry.getValue(SOURCE_KIND);
+    if (kind == SourceKind.LIBRARY) {
+      return SourcePriority.LIBRARY;
+    } else if (kind == SourceKind.PART) {
+      return SourcePriority.NORMAL_PART;
+    }
+    return SourcePriority.UNKNOWN;
+  }
+
+  Object /*V*/ _computeResult(
+      AnalysisTarget target, ResultDescriptor /*<V>*/ descriptor) {
+    cache.CacheEntry entry = _cache.get(target);
+    if (entry == null) {
+      return descriptor.defaultValue;
+    }
+    if (descriptor is CompositeResultDescriptor) {
+      List compositeResults = [];
+      for (ResultDescriptor descriptor in descriptor.contributors) {
+        List value = _computeResult(target, descriptor);
+        compositeResults.addAll(value);
+      }
+      return compositeResults;
+    }
+    CacheState state = entry.getState(descriptor);
+    if (state == CacheState.FLUSHED || state == CacheState.INVALID) {
+      _driver.computeResult(target, descriptor);
+    }
+    return entry.getValue(descriptor);
+  }
+
+  /**
+   * Given the encoded form of a source ([encoding]), use the source factory to
+   * reconstitute the original source.
+   */
+  Source _computeSourceFromEncoding(String encoding) =>
+      _sourceFactory.fromEncoding(encoding);
+
+  /**
+   * Return `true` if the given list of [sources] contains the given
+   * [targetSource].
+   */
+  bool _contains(List<Source> sources, Source targetSource) {
+    for (Source source in sources) {
+      if (source == targetSource) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  /**
+   * Return `true` if the given list of [sources] contains any of the given
+   * [targetSources].
+   */
+  bool _containsAny(List<Source> sources, List<Source> targetSources) {
+    for (Source targetSource in targetSources) {
+      if (_contains(sources, targetSource)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  /**
+   * Set the contents of the given [source] to the given [contents] and mark the
+   * source as having changed. The additional [offset], [oldLength] and
+   * [newLength] information is used by the context to determine what reanalysis
+   * is necessary. The method [setChangedContents] triggers a source changed
+   * event where as this method does not.
+   */
+  bool _contentRangeChanged(Source source, String contents, int offset,
+      int oldLength, int newLength) {
+    bool changed = false;
+    String originalContents = _contentCache.setContents(source, contents);
+    if (contents != null) {
+      if (contents != originalContents) {
+        // TODO(brianwilkerson) Find a better way to do incremental analysis.
+//        if (_options.incremental) {
+//          _incrementalAnalysisCache = IncrementalAnalysisCache.update(
+//              _incrementalAnalysisCache, source, originalContents, contents,
+//              offset, oldLength, newLength, _cache.get(source));
+//        }
+        _sourceChanged(source);
+        changed = true;
+        cache.CacheEntry entry = _cache.get(source);
+        if (entry != null) {
+          entry.modificationTime = _contentCache.getModificationStamp(source);
+          entry.setValue(CONTENT, contents);
+        }
+      }
+    } else if (originalContents != null) {
+      _incrementalAnalysisCache =
+          IncrementalAnalysisCache.clear(_incrementalAnalysisCache, source);
+      _sourceChanged(source);
+      changed = true;
+    }
+    return changed;
+  }
+
+  /**
+   * Set the contents of the given [source] to the given [contents] and mark the
+   * source as having changed. This has the effect of overriding the default
+   * contents of the source. If the contents are `null` the override is removed
+   * so that the default contents will be returned. If [notify] is true, a
+   * source changed event is triggered.
+   */
+  void _contentsChanged(Source source, String contents, bool notify) {
+    String originalContents = _contentCache.setContents(source, contents);
+    handleContentsChanged(source, originalContents, contents, notify);
+  }
+
+  /**
+   * Create a cache entry for the given [source]. The source was explicitly
+   * added to this context if [explicitlyAdded] is `true`. Return the cache
+   * entry that was created.
+   */
+  cache.CacheEntry _createCacheEntry(Source source, bool explicitlyAdded) {
+    cache.CacheEntry entry = new cache.CacheEntry();
+    entry.modificationTime = getModificationStamp(source);
+    entry.explicitlyAdded = explicitlyAdded;
+    _cache.put(source, entry);
+    return entry;
+  }
+
+  /**
+   * Return a list containing all of the change notices that are waiting to be
+   * returned. If there are no notices, then return either `null` or an empty
+   * list, depending on the value of [nullIfEmpty].
+   */
+  List<ChangeNotice> _getChangeNotices(bool nullIfEmpty) {
+    if (_pendingNotices.isEmpty) {
+      if (nullIfEmpty) {
+        return null;
+      }
+      return ChangeNoticeImpl.EMPTY_ARRAY;
+    }
+    List<ChangeNotice> notices = new List.from(_pendingNotices.values);
+    _pendingNotices.clear();
+    return notices;
+  }
+
+  /**
+   * Return a change notice for the given [source], creating one if one does not
+   * already exist.
+   */
+  ChangeNoticeImpl _getNotice(Source source) {
+    // Used in commented out code.
+    ChangeNoticeImpl notice = _pendingNotices[source];
+    if (notice == null) {
+      notice = new ChangeNoticeImpl(source);
+      _pendingNotices[source] = notice;
+    }
+    return notice;
+  }
+
+  Object _getResult(AnalysisTarget target, ResultDescriptor descriptor) {
+    cache.CacheEntry entry = _cache.get(target);
+    if (entry != null && entry.isValid(descriptor)) {
+      return entry.getValue(descriptor);
+    }
+    return descriptor.defaultValue;
+  }
+
+  /**
+   * Return a list containing all of the sources known to this context that have
+   * the given [kind].
+   */
+  List<Source> _getSources(SourceKind kind) {
+    List<Source> sources = new List<Source>();
+    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+    while (iterator.moveNext()) {
+      if (iterator.value.getValue(SOURCE_KIND) == kind &&
+          iterator.key is Source) {
+        sources.add(iterator.key);
+      }
+    }
+    return sources;
+  }
+
+  /**
+   * Look at the given [source] to see whether a task needs to be performed
+   * related to it. If so, add the source to the set of sources that need to be
+   * processed. This method is intended to be used for testing purposes only.
+   */
+  void _getSourcesNeedingProcessing(Source source, cache.CacheEntry sourceEntry,
+      bool isPriority, bool hintsEnabled, bool lintsEnabled,
+      HashSet<Source> sources) {
+    CacheState state = sourceEntry.getState(CONTENT);
+    if (state == CacheState.INVALID ||
+        (isPriority && state == CacheState.FLUSHED)) {
+      sources.add(source);
+      return;
+    } else if (state == CacheState.ERROR) {
+      return;
+    }
+    state = sourceEntry.getState(SOURCE_KIND);
+    if (state == CacheState.INVALID ||
+        (isPriority && state == CacheState.FLUSHED)) {
+      sources.add(source);
+      return;
+    } else if (state == CacheState.ERROR) {
+      return;
+    }
+    SourceKind kind = sourceEntry.getValue(SOURCE_KIND);
+    if (kind == SourceKind.LIBRARY || kind == SourceKind.PART) {
+      state = sourceEntry.getState(SCAN_ERRORS);
+      if (state == CacheState.INVALID ||
+          (isPriority && state == CacheState.FLUSHED)) {
+        sources.add(source);
+        return;
+      } else if (state == CacheState.ERROR) {
+        return;
+      }
+      state = sourceEntry.getState(PARSE_ERRORS);
+      if (state == CacheState.INVALID ||
+          (isPriority && state == CacheState.FLUSHED)) {
+        sources.add(source);
+        return;
+      } else if (state == CacheState.ERROR) {
+        return;
+      }
+//      if (isPriority) {
+//        if (!sourceEntry.hasResolvableCompilationUnit) {
+//          sources.add(source);
+//          return;
+//        }
+//      }
+      for (Source librarySource in getLibrariesContaining(source)) {
+        cache.CacheEntry libraryEntry = _cache.get(librarySource);
+        state = libraryEntry.getState(LIBRARY_ELEMENT);
+        if (state == CacheState.INVALID ||
+            (isPriority && state == CacheState.FLUSHED)) {
+          sources.add(source);
+          return;
+        } else if (state == CacheState.ERROR) {
+          return;
+        }
+        cache.CacheEntry unitEntry =
+            _cache.get(new LibrarySpecificUnit(librarySource, source));
+        state = unitEntry.getState(RESOLVED_UNIT);
+        if (state == CacheState.INVALID ||
+            (isPriority && state == CacheState.FLUSHED)) {
+          sources.add(source);
+          return;
+        } else if (state == CacheState.ERROR) {
+          return;
+        }
+        if (_shouldErrorsBeAnalyzed(source, unitEntry)) {
+          state = unitEntry.getState(VERIFY_ERRORS);
+          if (state == CacheState.INVALID ||
+              (isPriority && state == CacheState.FLUSHED)) {
+            sources.add(source);
+            return;
+          } else if (state == CacheState.ERROR) {
+            return;
+          }
+          if (hintsEnabled) {
+            state = unitEntry.getState(HINTS);
+            if (state == CacheState.INVALID ||
+                (isPriority && state == CacheState.FLUSHED)) {
+              sources.add(source);
+              return;
+            } else if (state == CacheState.ERROR) {
+              return;
+            }
+          }
+//          if (lintsEnabled) {
+//            state = unitEntry.getState(LINTS);
+//            if (state == CacheState.INVALID ||
+//                (isPriority && state == CacheState.FLUSHED)) {
+//              sources.add(source);
+//              return;
+//            } else if (state == CacheState.ERROR) {
+//              return;
+//            }
+//          }
+        }
+      }
+//    } else if (kind == SourceKind.HTML) {
+//      CacheState parsedUnitState = sourceEntry.getState(HtmlEntry.PARSED_UNIT);
+//      if (parsedUnitState == CacheState.INVALID ||
+//          (isPriority && parsedUnitState == CacheState.FLUSHED)) {
+//        sources.add(source);
+//        return;
+//      }
+//      CacheState resolvedUnitState =
+//          sourceEntry.getState(HtmlEntry.RESOLVED_UNIT);
+//      if (resolvedUnitState == CacheState.INVALID ||
+//          (isPriority && resolvedUnitState == CacheState.FLUSHED)) {
+//        sources.add(source);
+//        return;
+//      }
+    }
+  }
+
+  /**
+   * Invalidate all of the resolution results computed by this context. The flag
+   * [invalidateUris] should be `true` if the cached results of converting URIs
+   * to source files should also be invalidated.
+   */
+  void _invalidateAllLocalResolutionInformation(bool invalidateUris) {
+    HashMap<Source, List<Source>> oldPartMap =
+        new HashMap<Source, List<Source>>();
+    // TODO(brianwilkerson) Implement this
+//    MapIterator<AnalysisTarget, cache.CacheEntry> iterator =
+//        _privatePartition.iterator();
+//    while (iterator.moveNext()) {
+//      AnalysisTarget target = iterator.key;
+//      cache.CacheEntry entry = iterator.value;
+//      if (entry is HtmlEntry) {
+//        HtmlEntry htmlEntry = entry;
+//        htmlEntry.invalidateAllResolutionInformation(invalidateUris);
+//        iterator.value = htmlEntry;
+//        _workManager.add(target, SourcePriority.HTML);
+//      } else if (entry is DartEntry) {
+//        DartEntry dartEntry = entry;
+//        oldPartMap[target] = dartEntry.getValue(DartEntry.INCLUDED_PARTS);
+//        dartEntry.invalidateAllResolutionInformation(invalidateUris);
+//        iterator.value = dartEntry;
+//        _workManager.add(target, _computePriority(dartEntry));
+//      }
+//    }
+    _removeFromPartsUsingMap(oldPartMap);
+  }
+
+  /**
+   * In response to a change to at least one of the compilation units in the
+   * library defined by the given [librarySource], invalidate any results that
+   * are dependent on the result of resolving that library.
+   *
+   * <b>Note:</b> Any cache entries that were accessed before this method was
+   * invoked must be re-accessed after this method returns.
+   */
+  void _invalidateLibraryResolution(Source librarySource) {
+    // TODO(brianwilkerson) Figure out whether we still need this.
+    // TODO(brianwilkerson) This could be optimized. There's no need to flush
+    // all of these entries if the public namespace hasn't changed, which will
+    // be a fairly common case. The question is whether we can afford the time
+    // to compute the namespace to look for differences.
+//    DartEntry libraryEntry = _getReadableDartEntry(librarySource);
+//    if (libraryEntry != null) {
+//      List<Source> includedParts =
+//          libraryEntry.getValue(DartEntry.INCLUDED_PARTS);
+//      libraryEntry.invalidateAllResolutionInformation(false);
+//      _workManager.add(librarySource, SourcePriority.LIBRARY);
+//      for (Source partSource in includedParts) {
+//        SourceEntry partEntry = _cache.get(partSource);
+//        if (partEntry is DartEntry) {
+//          partEntry.invalidateAllResolutionInformation(false);
+//        }
+//      }
+//    }
+  }
+
+  /**
+   * Log the given debugging [message].
+   */
+  void _logInformation(String message) {
+    AnalysisEngine.instance.logger.logInformation(message);
+  }
+
+  /**
+   * Notify all of the analysis listeners that the errors associated with the
+   * given [source] has been updated to the given [errors].
+   */
+  void _notifyErrors(
+      Source source, List<AnalysisError> errors, LineInfo lineInfo) {
+    int count = _listeners.length;
+    for (int i = 0; i < count; i++) {
+      _listeners[i].computedErrors(this, source, errors, lineInfo);
+    }
+  }
+
+  /**
+   * Remove the given libraries that are keys in the given map from the list of
+   * containing libraries for each of the parts in the corresponding value.
+   */
+  void _removeFromPartsUsingMap(HashMap<Source, List<Source>> oldPartMap) {
+    // TODO(brianwilkerson) Figure out whether we still need this.
+//    oldPartMap.forEach((Source librarySource, List<Source> oldParts) {
+//      for (int i = 0; i < oldParts.length; i++) {
+//        Source partSource = oldParts[i];
+//        if (partSource != librarySource) {
+//          DartEntry partEntry = _getReadableDartEntry(partSource);
+//          if (partEntry != null) {
+//            partEntry.removeContainingLibrary(librarySource);
+//            if (partEntry.containingLibraries.length == 0 &&
+//                !exists(partSource)) {
+//              _cache.remove(partSource);
+//            }
+//          }
+//        }
+//      }
+//    });
+  }
+
+  /**
+   * Remove the given [source] from the priority order if it is in the list.
+   */
+  void _removeFromPriorityOrder(Source source) {
+    int count = _priorityOrder.length;
+    List<Source> newOrder = new List<Source>();
+    for (int i = 0; i < count; i++) {
+      if (_priorityOrder[i] != source) {
+        newOrder.add(_priorityOrder[i]);
+      }
+    }
+    if (newOrder.length < count) {
+      analysisPriorityOrder = newOrder;
+    }
+  }
+
+  /**
+   * Return `true` if errors should be produced for the given [source]. The
+   * [entry] associated with the source is passed in for efficiency.
+   */
+  bool _shouldErrorsBeAnalyzed(Source source, cache.CacheEntry entry) {
+    if (source.isInSystemLibrary) {
+      return _options.generateSdkErrors;
+    } else if (!entry.explicitlyAdded) {
+      return _options.generateImplicitErrors;
+    } else {
+      return true;
+    }
+  }
+
+  /**
+   * Create an entry for the newly added [source] and invalidate any sources
+   * that referenced the source before it existed.
+   */
+  void _sourceAvailable(Source source) {
+    cache.CacheEntry entry = _cache.get(source);
+    if (entry == null) {
+      _createCacheEntry(source, true);
+    } else {
+      // TODO(brianwilkerson) Implement this.
+//      _propagateInvalidation(source, entry);
+    }
+  }
+
+  /**
+   * Invalidate the [source] that was changed and any sources that referenced
+   * the source before it existed.
+   */
+  void _sourceChanged(Source source) {
+    cache.CacheEntry entry = _cache.get(source);
+    // If the source is removed, we don't care about it.
+    if (entry == null) {
+      return;
+    }
+    // Check whether the content of the source is the same as it was the last
+    // time.
+    String sourceContent = entry.getValue(CONTENT);
+    if (sourceContent != null) {
+      entry.setState(CONTENT, CacheState.FLUSHED);
+      try {
+        TimestampedData<String> fileContents = getContents(source);
+        if (fileContents.data == sourceContent) {
+          return;
+        }
+      } catch (e) {}
+    }
+    // We need to invalidate the cache.
+    // TODO(brianwilkerson) Implement this.
+//    _propagateInvalidation(source, entry);
+  }
+
+  /**
+   * Record that the give [source] has been deleted.
+   */
+  void _sourceDeleted(Source source) {
+    // TODO(brianwilkerson) Implement this.
+//    SourceEntry sourceEntry = _cache.get(source);
+//    if (sourceEntry is HtmlEntry) {
+//      HtmlEntry htmlEntry = sourceEntry;
+//      htmlEntry.recordContentError(new CaughtException(
+//          new AnalysisException("This source was marked as being deleted"),
+//          null));
+//    } else if (sourceEntry is DartEntry) {
+//      DartEntry dartEntry = sourceEntry;
+//      HashSet<Source> libraries = new HashSet<Source>();
+//      for (Source librarySource in getLibrariesContaining(source)) {
+//        libraries.add(librarySource);
+//        for (Source dependentLibrary
+//            in getLibrariesDependingOn(librarySource)) {
+//          libraries.add(dependentLibrary);
+//        }
+//      }
+//      for (Source librarySource in libraries) {
+//        _invalidateLibraryResolution(librarySource);
+//      }
+//      dartEntry.recordContentError(new CaughtException(
+//          new AnalysisException("This source was marked as being deleted"),
+//          null));
+//    }
+    _removeFromPriorityOrder(source);
+  }
+
+  /**
+   * Record that the given [source] has been removed.
+   */
+  void _sourceRemoved(Source source) {
+    List<Source> containingLibraries = getLibrariesContaining(source);
+    if (containingLibraries != null && containingLibraries.isNotEmpty) {
+      HashSet<Source> libraries = new HashSet<Source>();
+      for (Source librarySource in containingLibraries) {
+        libraries.add(librarySource);
+        for (Source dependentLibrary
+            in getLibrariesDependingOn(librarySource)) {
+          libraries.add(dependentLibrary);
+        }
+      }
+      for (Source librarySource in libraries) {
+        _invalidateLibraryResolution(librarySource);
+      }
+    }
+    _cache.remove(source);
+    _removeFromPriorityOrder(source);
+  }
+
+  /**
+   * TODO(scheglov) A hackish, limited incremental resolution implementation.
+   */
+  bool _tryPoorMansIncrementalResolution(Source unitSource, String newCode) {
+    // TODO(brianwilkerson) Implement this.
+    return false;
+//    return PerformanceStatistics.incrementalAnalysis.makeCurrentWhile(() {
+//      incrementalResolutionValidation_lastUnitSource = null;
+//      incrementalResolutionValidation_lastLibrarySource = null;
+//      incrementalResolutionValidation_lastUnit = null;
+//      // prepare the entry
+//      cache.CacheEntry entry = _cache.get(unitSource);
+//      if (entry == null) {
+//        return false;
+//      }
+//      // prepare the (only) library source
+//      List<Source> librarySources = getLibrariesContaining(unitSource);
+//      if (librarySources.length != 1) {
+//        return false;
+//      }
+//      Source librarySource = librarySources[0];
+//      // prepare the library element
+//      LibraryElement libraryElement = getLibraryElement(librarySource);
+//      if (libraryElement == null) {
+//        return false;
+//      }
+//      // prepare the existing unit
+//      CompilationUnit oldUnit =
+//          getResolvedCompilationUnit2(unitSource, librarySource);
+//      if (oldUnit == null) {
+//        return false;
+//      }
+//      // do resolution
+//      Stopwatch perfCounter = new Stopwatch()..start();
+//      PoorMansIncrementalResolver resolver = new PoorMansIncrementalResolver(
+//          typeProvider, unitSource, entry, oldUnit,
+//          analysisOptions.incrementalApi, analysisOptions);
+//      bool success = resolver.resolve(newCode);
+//      AnalysisEngine.instance.instrumentationService.logPerformance(
+//          AnalysisPerformanceKind.INCREMENTAL, perfCounter,
+//          'success=$success,context_id=$_id,code_length=${newCode.length}');
+//      if (!success) {
+//        return false;
+//      }
+//      // if validation, remember the result, but throw it away
+//      if (analysisOptions.incrementalValidation) {
+//        incrementalResolutionValidation_lastUnitSource = oldUnit.element.source;
+//        incrementalResolutionValidation_lastLibrarySource =
+//            oldUnit.element.library.source;
+//        incrementalResolutionValidation_lastUnit = oldUnit;
+//        return false;
+//      }
+//      // prepare notice
+//      {
+//        LineInfo lineInfo = getLineInfo(unitSource);
+//        ChangeNoticeImpl notice = _getNotice(unitSource);
+//        notice.resolvedDartUnit = oldUnit;
+//        notice.setErrors(entry.allErrors, lineInfo);
+//      }
+//      // OK
+//      return true;
+//    });
+  }
+
+  /**
+   * Check the cache for any invalid entries (entries whose modification time
+   * does not match the modification time of the source associated with the
+   * entry). Invalid entries will be marked as invalid so that the source will
+   * be re-analyzed. Return `true` if at least one entry was invalid.
+   */
+  bool _validateCacheConsistency() {
+    int consistencyCheckStart = JavaSystem.nanoTime();
+    List<AnalysisTarget> changedTargets = new List<AnalysisTarget>();
+    List<AnalysisTarget> missingTargets = new List<AnalysisTarget>();
+    MapIterator<AnalysisTarget, cache.CacheEntry> iterator = _cache.iterator();
+    while (iterator.moveNext()) {
+      AnalysisTarget target = iterator.key;
+      cache.CacheEntry entry = iterator.value;
+      if (target is Source) {
+        int sourceTime = getModificationStamp(target);
+        if (sourceTime != entry.modificationTime) {
+          changedTargets.add(target);
+        }
+      }
+      if (entry.exception != null) {
+        if (!exists(target)) {
+          missingTargets.add(target);
+        }
+      }
+    }
+    int count = changedTargets.length;
+    for (int i = 0; i < count; i++) {
+      _sourceChanged(changedTargets[i]);
+    }
+    int removalCount = 0;
+    for (AnalysisTarget target in missingTargets) {
+      if (target is Source &&
+          getLibrariesContaining(target).isEmpty &&
+          getLibrariesDependingOn(target).isEmpty) {
+        _cache.remove(target);
+        removalCount++;
+      }
+    }
+    int consistencyCheckEnd = JavaSystem.nanoTime();
+    if (changedTargets.length > 0 || missingTargets.length > 0) {
+      StringBuffer buffer = new StringBuffer();
+      buffer.write("Consistency check took ");
+      buffer.write((consistencyCheckEnd - consistencyCheckStart) / 1000000.0);
+      buffer.writeln(" ms and found");
+      buffer.write("  ");
+      buffer.write(changedTargets.length);
+      buffer.writeln(" inconsistent entries");
+      buffer.write("  ");
+      buffer.write(missingTargets.length);
+      buffer.write(" missing sources (");
+      buffer.write(removalCount);
+      buffer.writeln(" removed");
+      for (Source source in missingTargets) {
+        buffer.write("    ");
+        buffer.writeln(source.fullName);
+      }
+      _logInformation(buffer.toString());
+    }
+    return changedTargets.length > 0;
+  }
+}
+
+/**
+ * A retention policy used by an analysis context.
+ */
+class ContextRetentionPolicy implements cache.CacheRetentionPolicy {
+  /**
+   * The context associated with this policy.
+   */
+  final AnalysisContextImpl context;
+
+  /**
+   * Initialize a newly created policy to be associated with the given
+   * [context].
+   */
+  ContextRetentionPolicy(this.context);
+
+  @override
+  RetentionPriority getAstPriority(
+      AnalysisTarget target, cache.CacheEntry entry) {
+    int priorityCount = context._priorityOrder.length;
+    for (int i = 0; i < priorityCount; i++) {
+      if (target == context._priorityOrder[i]) {
+        return RetentionPriority.HIGH;
+      }
+    }
+    if (_astIsNeeded(entry)) {
+      return RetentionPriority.MEDIUM;
+    }
+    return RetentionPriority.LOW;
+  }
+
+  bool _astIsNeeded(cache.CacheEntry entry) =>
+      entry.isInvalid(BUILD_FUNCTION_TYPE_ALIASES_ERRORS) ||
+          entry.isInvalid(BUILD_LIBRARY_ERRORS) ||
+          entry.isInvalid(CONSTRUCTORS_ERRORS) ||
+          entry.isInvalid(HINTS) ||
+          //entry.isInvalid(LINTS) ||
+          entry.isInvalid(RESOLVE_REFERENCES_ERRORS) ||
+          entry.isInvalid(RESOLVE_TYPE_NAMES_ERRORS) ||
+          entry.isInvalid(VERIFY_ERRORS);
+}
+
+/**
+ * An object that manages the partitions that can be shared between analysis
+ * contexts.
+ */
+class PartitionManager {
+  /**
+   * The default cache size for a Dart SDK partition.
+   */
+  static int _DEFAULT_SDK_CACHE_SIZE = 256;
+
+  /**
+   * A table mapping SDK's to the partitions used for those SDK's.
+   */
+  HashMap<DartSdk, cache.SdkCachePartition> _sdkPartitions =
+      new HashMap<DartSdk, cache.SdkCachePartition>();
+
+  /**
+   * Clear any cached data being maintained by this manager.
+   */
+  void clearCache() {
+    _sdkPartitions.clear();
+  }
+
+  /**
+   * Return the partition being used for the given [sdk], creating the partition
+   * if necessary.
+   */
+  cache.SdkCachePartition forSdk(DartSdk sdk) {
+    // Call sdk.context now, because when it creates a new
+    // InternalAnalysisContext instance, it calls forSdk() again, so creates an
+    // SdkCachePartition instance.
+    // So, if we initialize context after "partition == null", we end up
+    // with two SdkCachePartition instances.
+    InternalAnalysisContext sdkContext = sdk.context;
+    // Check cache for an existing partition.
+    cache.SdkCachePartition partition = _sdkPartitions[sdk];
+    if (partition == null) {
+      partition =
+          new cache.SdkCachePartition(sdkContext, _DEFAULT_SDK_CACHE_SIZE);
+      _sdkPartitions[sdk] = partition;
+    }
+    return partition;
+  }
+}